Multi-layered golf ball and composition

ABSTRACT

The present invention is directed towards a multi-layer golf ball which comprises a core, a cover layer and at least one intermediate layer disposed between the core and cover, wherein the intermediate layer comprises a glycidyl polymer and optionally, a second thermoplastic component such as polyetherester block copolymer, polyesterester block copolymer, polyetheramide block copolymer, dynamically vulcanized thermoplastic elastomer, functionalized styrene-butadiene elastomer, thermoplastic polyurethane, thermoplastic polyesters, metallocenie polymer or blends thereof and a density-modifying filler such as zinc oxide, titanium dioxide or blends thereof. Further, in a preferred embodiment, the core has a compression less than 60, the finished ball has a COR of greater than about 0.78, the intermediate layer has a specific gravity of greater than about 1.2 and the cover has a Shore D hardness of about 54 to about 72.

FIELD OF THE INVENTION

This invention relates generally to golf balls, and more specifically,to a multi-layer golf ball and a composition therefore. In particular,this invention relates to a golf ball having a core, a cover and atleast one intermediate layer disposed between the core and cover,wherein the intermediate layer is formed from a blend comprising atleast one glycidyl polymer. The multi-layer golf balls of the presentinvention have been found to provide good distance, durability, anddesirable playing characteristics.

BACKGROUND OF THE INVENTION

Conventional golf balls can be divided into two general types or groups:solid balls or wound balls. The difference in play characteristicsresulting from these different types of constructions can be quitesignificant.

Balls having a solid construction are generally most popular with theaverage recreational golfer because they provide a very durable ballwhile also providing maximum distance. Solid balls are made with a solidcore, usually formed of a crosslinked rubber, which is encased by acover material. Typically the solid core is formed of polybutadienewhich is chemically crosslinked with zinc diacrylate and/or similarcrosslinking agents and is covered by a tough, cut-proof blended cover.The cover is generally formed of a material such as SURLYN, which is atrademark for an ionomer resin produced by DuPont of Wilmington, Del.The combination of the core and cover materials provide a ball that isvirtually indestructible by golfers. Further, such a combination impartsa high initial velocity to the ball which results in improved distance.Because the materials of which the ball is formed are very rigid, solidballs generally have a hard “feel” when struck with a club. Likewise,due to their hardness, these balls have a relatively low spin rate whichprovides greater distance.

At the present time, the wound ball remains the preferred ball of moreadvanced players due to its spin and feel characteristics. Wound ballstypically have either a solid rubber or liquid center core around whichmany yards of a stretched elastic thread or yarn are wound. The woundcore is then covered with a durable cover material such as a SURLYN orsimilar material or a softer cover such as balata or polyurethane. Woundballs are generally softer and provide more spin than non-wound balls,which enables a skilled golfer to have more control over the ball'sflight and final position. Particularly, with approach shots into thegreen, the high spin rate of soft, wound balls enables the golfer tostop the ball very near its landing position.

A number of patents have been issued that arc directed towards modifyingthe properties of a conventional solid ball by altering the typicalsingle layer core and single cover layer construction to provide amulti-layer ball having Such as a dual cover layer, dual core layerand/or a ball having a mantle layer disposed between the cover and thecore. The inventions disclosed in the prior art patents arc directedtowards improving a variety of golf balls physical properties that helpdetermine “in-play” characteristics.

Several patents are directed towards improving the carry distance ofsuch balls. For example, U.S. Pat. No. 4,863,167 relates to a threepiece solid golfball having increased flight distance, wherein the ballhas a center portion and an outer layer formed from a rubbercomposition, wherein the outer layer is harder than the center portionand further contains a gravity-adjusting filler so as to impart a higherspecific gravity to the outer layer than that of the center portion.U.S. Pat. No. 5,184,828 relates to a solid three-piece golf ball havingimproved rebound characteristics and carry distance while maintaining anadequate spin rate, wherein these characteristics are allegedly obtainedby controlling the size of the polybutadiene inner core and outer layeras well as their specific gravity and hardness. According to the '828patent, the key to obtaining the desired rebound characteristics is thatthe maximum hardness (42-62 Shore D) must be located at the interfacebetween the core and the mantle and the hardness must then decrease bothinwardly and outwardly. U.S. Pat. No. 4,714,253 is also directed towardsa three-piece golf ball having an improved rebound coefficient. Thisgolf ball has a core with a Shore C hardness of 57-80 in its center, butnot more than 83 at a distance between 5-10 mm from its center and anouter layer with a Shore C hardness of 70-83.

Additionally, there are a number of patents directed towards improvingthe spin and feel of solid balls while maintaining the distance providedby the solid construction. For example, U.S. Pat. No. 5,072,944discloses a three-piece solid golf ball having a center layer and anouter layer that are prepared from a rubber composition, wherein it isdesirable that the center core layer is softer than the outer layer, thelayers having a hardness (Shore C) of 25-50 and 70-90, respectively.

U.S. Pat. No. 4,625,964 relates to a solid golf ball having apolybutadiene rubber core of a diameter not more than 32 mm, apolybutadiene rubber intermediate layer having a specific gravity oflower than that of the core material, and a cover. U.S. Pat. No.4,650,193 is directed towards a solid golf ball having a core comprisinga central portion and an integral outer layer, wherein the core is acurable elastomer such as polybutadiene which is treated with a curealtering agent to soften an outer layer of the core, to produce acentral layer with a hardness (Shore C) of greater than 75 and an outerlayer with a hardness (Shore A) of less than 80.

U.S. Pat. No. 4,848,770 discloses a solid three-piece golfball whichincludes a core of a highly filled synthetic rubber or polymericmaterial, an intermediate mantle of an unfilled synthetic rubber and acover. The core and intermediate mantle have a hardness of between 50-95Shore D. U.S. Pat. No. 5,002,281 is directed towards a three-piece solidgolf ball which has an inner core having a hardness of 25-70 (Shore C),an outer shell having a hardness of 80-95 (Shore C) and a cover.Further, the specific gravity of the inner core must be greater than1.0, but less than or equal to that of the outer shell, which must beless than 1.3.

The prior art discloses a variety of materials other than polybutadienefor use as intermediate layers. For example, U.S. Pat. No. 5,253,871concerns a golf ball having a three-piece structure comprising anelastomer core, an intermediate layer of a thermoplastic materialcontaining at least 10% of ether block copolymer, preferably blendedwith an ionomer, and a thermoplastic cover. U.S. Pat. No. 5,681,898 isdirected to a multilayer golf ball having a conventional polybutadienecore, an ionomer cover and an intermediate layer formed from a blend ofan ethylene methacrylic acid copolymer and a vulcanizate formed frompolybutadiene and a peroxide curing agent. U.S. Pat. Nos. 5,439,227 and5,556,098 both disclose multilayer golf balls which have a conventionalpolybutadiene core, conventional covers and an intermediate layer formedfrom a polyetherester block copolymer blended with an ionomer.

Further, there are also several patents which are directed to golf ballshaving multiple cover layers. For example U.S. Pat. No. 4,431,193relates to a golf ball having a multilayer cover wherein the inner layeris a hard, high flexural modulus ionomer resin and the outer layer is asoft, low flexural modulus ionomer resin, and wherein either or bothlayers may comprise a foamed ionomer resin. U.S. Pat. No. 5,314,187 alsorelates to golf balls having a multiple layer cover, wherein the outerlayer is molded over the inner layer and comprises a blend of balata andan elastomer and the inner layer is an ionomer resin. U.S. Pat. No.4,919,434 is directed towards a golf ball having a cover which comprisesan inner layer and an outer layer, each of which comprise athermoplastic resin. Preferably the layers are comprised of materialsthat are capable of bonding with each other, for example, by heat, or byother means which are readily known to one of ordinary skill in the art.

Additionally, U.S. Pat. No. 5,631,324 is directed to a golf ball whereinthe terpolymer composition of the core, mantle layers, or covercomprises an epoxy (i.e., glycidyl moiety) and an ionomer material. U.S.Pat. No. 5,155,157 provides compositions useful in the manufacture ofone-, two- and three-piece golf balls that comprises blends of blockcopolymers, an ionomer material, and an epoxy-containing compound. U.S.Pat. No. 5,565,524 provides a golf ball having a cover that comprises anionomer material and a glycidyl-group-containing olefinic copolymer.U.S. Pat. No. 5,543,467 discloses a golf ball having a core and a coverin which the base material of the cover comprises a maleicanhydride-modified olefinic copolymer, an ionomer resin, and aglycidyl-group-containing olefinic copolymer.

However, none of the patents discussed above disclose the multi-layerball of the current invention that employs the materials, and has theimproved golf ball properties, as disclosed herein.

SUMMARY OF THE INVENTION

The present invention is directed towards an improved multi-layer golfball which includes a core having a compression of no greater than about90, a cover layer having a Shore D hardness of about 54 to 72, and atleast one intermediate layer disposed between the cover and the core,wherein the at least one intermediate layer is formed from a blendincluding a glycidyl polymer and the golf ball has a coefficient ofrestitution of greater than about 0.76.

In one embodiment, the blend further includes a second component,wherein the second component is a thermoplastic material. In anotherembodiment, the second component is selected from the group consistingof polyesterester block copolymers, polyetherester block copolymers,polyetheramide block copolymers, dynamically vulcanized thermoplasticelastomers, styrene-butadiene elastomers, thermoplastic polyurethanes,thermoplastic polyesters, polymers formed using a metallocene catalyst,and blends thereof. Preferably, the second component includes apolyetherester block copolymer. In another embodiment, the blend furtherincludes a filler in an amount sufficient to provide the at least oneintermediate layer with a specific gravity of greater than about 1.2. Instill another embodiment, the intermediate layer has a specific gravityof greater than about 1.25. In yet another embodiment, the fillerincludes zinc oxide.

In another embodiment, the blend includes about 10 to about 50 percentby weight lycidyl polymer, about 25 to 75 percent by weight secondthermoplastic component and about 5 to about 40 percent by weightfiller. Preferably, the blend includes about 15 to 30 percent by weightglycidyl polymer, about 40 to 70 percent by weight second thermoplasticcomponent and about 15 to 30 percent by weight filler. In anotherembodiment, the intermediate layer has a Shore D hardness of about 35 to50 and a flexural modulus of about 1,000 psi to 8,000 psi. In anotherembodiment, the golf ball has a compression of no greater than about 90.In still another embodiment, the cover includes at least one of athermoplastic or a thermoset material.

The present invention is also directed to a golf ball having a coreincluding polybutadiene, a cover layer having a Shore D hardness ofabout 54 to 72, and at least one intermediate layer disposed between thecover and the core, wherein the at least one intermediate layer isformed from a blend including about 15 to 30 weight percent of aglycidyl polymer, about 15 to 30 weight percent zinc oxide, up to about70 weight percent polyetherester block copolymer; and wherein the golfball has a coefficient of restitution of greater than about 0.78.

In one embodiment, the core blend further includes calcium oxide.Additionally, the intermediate layer is formed from a blend includingabout 19 to 21 weight percent glycidyl polymer, about 20 to 22 weightpercent zinc oxide, and about 58 to 60 weight percent polyetheresterblock copolymer. In another embodiment, the intermediate layer has aShore D hardness of less than about 40 and a flexural modulus of lessthan about 10,000 psi. In still another embodiment, the blend includesat least about 40 weight percent polyetherester block copolymer.

The present invention is also directed to a golf ball having acoefficient of restitution of greater than about 0.7 and a compressionof at least about 50, wherein the ball includes a core and a coverhaving at least one layer disposed concentrically about the core,wherein the layer is a composition including a glycidyl polymercomposition and a thermoplastic, selected from the group ofcopolyesters, polyamides, polyetherester block copolymers,polyesterester block copolymers, polyetheramide block copolymers,polyesteramide block copolymers, and polyurethane, wherein the materialhas a flexural modulus less than 20,000 psi.

In one embodiment, the material includes a filler sufficient to producea specific gravity of greater than about 1.2. In another embodiment, theglycidyl polymer composition comprises at least one repeat unit offormula 1:

wherein R₁, is hydrogen, linear or branched alkyl group having theformula C_(x)H_(2x+1), aromatic, or alicyclic, where x is an integerfrom 1 to about 8; R₂ is hydrogen, linear or branched alkyl group havingthe formula C_(y)H_(2y+1), aromatic, or alicyclic, where y is an integerfrom 1 to about 20; and n is an integer ranging from 1 to about 6.

In another embodiment, the glycidyl polymer composition includes arepeat unit of formula 2:

wherein R₃, R₄, and R₅ are hydrogen, linear or branched alkyl grouphaving the formula C_(x)H_(2x+1), aromatic, or alicyclic, where x is aninteger from 1 to about 8; R₆ is hydrogen, linear or branched alkylgroup having the formula C_(y)H_(2y+1), aromatic, or alicyclic, where yis an integer from 1 to about 20; o ranges from about 1 to about 99weight percent of the total glycidyl polymer; p ranges from about 99 toabout 1 weight percent of the total glycidyl polymer; and q is aninteger ranging from 1 to about 6.

In still another embodiment, the glycidyl polymer composition includes arepeat unit of formula 3:

wherein R₇, R₈, R₉, and R₁₁ are hydrogen, linear or branched alkyl grouphaving the formula C_(x)H_(2x+1), aromatic, or alicyclic, where x is aninteger from 1 to about 8; R₁₀ and R₁₂ are hydrogen, linear or branchedalkyl group having the formula C_(y)H_(2y+1), aromatic, or alicyclic,where y is an integer from 1 to about 20; r ranges from about 1 to about99 weight percent of the total glycidyl polymer; s ranges from about 1to about 50 weight percent of the total glycidyl polymer; t ranges fromabout 1 to about 30 weight percent of the total glycidyl polymer; and uis an integer ranging from about 1 to about 6.

In one embodiment, the cover includes an outer layer and an inner layerand the composition forms the inner layer. In another embodiment, theinner layer has a first hardness and the outer layer has a secondhardness greater than the first hardness. In still another embodiment,the core has a third hardness within 10 Shore D of the first hardnessand less than the second hardness.

In another embodiment, the inner layer has a specific gravity greaterthan about 1.2 In another embodiment, the inner layer has a flexuralmodulus of less than about 10,000 psi.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following terms that are used in this application are defined interms of the enumerated ASTM tests: Specific Gravity ASTM D-297,Flexural (Flex) Modulus ASTM D-790, Shore D Hardness ASTM D-2240, andShore C Hardness ASTM D-2240. The ASTM D-297 test was carried out in labconditions where the temperature was controlled to 20-23° C.

As used herein, the terns “points” or “compression points” refer to thecompression scale or the compression scale based on the ATTI EngineeringCompression Tester. This scale, which is well known to those working inthis field, is used in determining the relative compression of a core orball.

As used herein, “COR” refers to Coefficient of Restitution, which isobtained by dividing a ball's rebound velocity by its initial (i.e.incomingi) velocity. This test is performed by firing the samples out ofan air cannon at a vertical steel plate over a range of test velocities(from 75 to 150 ft./sec.). A golf ball having a high COR dissipates asmaller fraction of its total energy when colliding with the plate andrebounding therefrom than does a ball with a lower COR. Unless otherwisenoted, the COR values reported herein are the values determined at anincoming velocity of 125 ft./sec.

As used herein, the term “glycidyl polymer” is defined as anyhomopolymer, copolymer, tepolymer, or mixture thereof, having at leastone glycidyl group in at least one of the monomer repeat units in thepolymer.

As used herein, the term “copolymer” refers to a polymer which is formedfrom two or more monomers, wherein said monomers are not identical.

As used herein, the term “terpolymer” refers to a polymer which isformed from three monomers, wherein said monomers are not identical.

As used herein, the term “pph” in connection with a batch formulationrefers parts by weight of the constituent per hundred parts of the basecomposition (e.g. elastomer).

The term “about,” as used herein in connection with one or more numbersor numerical ranges, should be understood to refer to all such numbers,including all numbers in a range.

The present invention is directed to an improved multilayer golf ballwhich comprises a core, a cover, and at least one intermediate layerdisposed between the core and the cover, wherein such golf ball providesa softer feel similar to a conventional wound ball, while also providingthe distance, durability and spin rates of a conventional two-pieceball. The cover is formed of at least one layer, for example, inner andouter cover layers. As discussed in detail below, the improvedmultilayer golf ball of the present invention is provided by forming aball having various structural components (e.g. cover, core,intermediate layer) each having desired properties and which may beformed from a variety of materials.

Many conventional two-piece “distance” golf balls are formed with coreshaving a high compression (e.g., greater than about 90) in order toachieve the desired high finished ball COR and initial velocitynecessary to obtain long overall distance for the ball. Balls havingSuch high compression cores typically have a hard feel when struck witha golf club.

However, the golf balls of the present invention are formed with a corehaving a low compression, but still exhibit a finished ball COR andinitial velocity approaching that of conventional two-piece distanceballs. Preferably, the cores employed in the golf balls of the presentinvention have a compression of less than about 60, more preferablyabout 45 to about 60 and most preferably about 50 to 55. Likewise, it ispreferred that the finished balls made with such cores have a COR,measured at an inbound speed of 125 ft./sec., of about 0.795 to about0.815, more preferably about 0.797 to about 0.812 and most preferablyabout 0.800 to about 0.810.

Additionally, it is preferred the core has a Shore C hardness of about65 to about 80, more preferably about 68 to about 75 and most preferablyabout 72 to about 75. Preferably, the core has a Shore D hardness within10 Shore D of the Shore D hardness of the intermediate layer.

The cores employed in the golf balls of the present invention preferablyhave a diameter of about 1.25 inches to about 1.51 inches, morepreferably about 1.30 inches to about 1.48 inches and most preferablyabout 1.39 inches. The overall diameter of the core and the intermediatelayer is about 84 percent to about 97 percent of the overall diameter ofthe finished ball.

A representative base composition for forming the cores employed in thepresent invention comprises polybutadiene and, in parts by weight basedon 100 parts polybutadiene, 20-50 parts of a metal salt of anα,β-unsaturated carboxylic acid, such as diacrylate, dimethacrylate, ormonomethacrylate. Preferably, the metal salt of an α,β-unsaturatedcarboxylic acid is zinc diacrylate. The polybutadiene preferably has acis- 1,4 content of above about 90% and more preferably above about 96%.Commercial sources of polybutadiene include SHELL 1220 manufactured byShell Chemical, NEOCIS BR40 manufactured by Enichem Elastomers, andUBEPOI, BR150 manufactured by Ube Industries, Ltd. If desired, thepolybutadiene can also be mixed with other elastomers known in the art,such as natural rubber, styrene butadiene, and/or isoprene in order tofurther modify the properties of the core. When a mixture of elastomersis used, the amounts of other constituents in the core composition areusually based on 100 parts by weight of the total elastomer mixture.

Metal salt diacrylates, dimethacrylates, and monomiietlhacrylatessuitable for use in the cores employed in this invention include thosewherein the metal is magnesium, calcium, zinc, aluminum, sodium, lithiumor nickel. Zinc diacrylate is preferred, because it provides golf ballswith a high initial velocity in the USGA test. The zinc diacrylate canbe of various grades of purity. For the purposes of this invention, thelower the quantity of zinc stearate present in the zinc diacrylate thehigher the zinc diacrylate purity. Zinc diacrylate containing less thanabout 10% zinc stearate is preferable. More preferable is zincdiacrylate containing about 4-8% zinc stearate. Suitable, commerciallyavailable zinc diacrylates include those from Sartomer. The preferredconcentrations of zinc diacrylate that can be used are 20-50 pph basedupon 100 pph of polybutadiene or alternately, polybutadiene with amixture of other elastomers that equal 100 pph.

Free radical initiators are used to promote cross-linking of the metalsalt diacrylate, dimethacrylate, or monomethacrylate and thepolybutadiene. Suitable free radical initiators for use in the inventioninclude, but are not limited to peroxide compounds, such as dicumylperoxide, 1,1-di(t-butylperoxy) 3,3,5-trimethyl cyclohexane,bis(t-butylperoxy) diusopropylbenzene, 2,5-dimethyl-2,5 di(t-butylperoxy) hexane, or di-t-butyl peroxide, and mixtures thereof.Other useful initiators would be readily apparent to one of ordinaryskill in the art without any need for experimentation. The initiator(s)at 100% activity are preferably added in an amount ranging between about0.05 and 2.5 pph based upon 100 parts of butadiene, or butadiene mixedwith one or more other elastomers. More preferably, the amount ofinitiator added ranges between about 0.15 and 2 pph and most preferablybetween about 0.25 and 1.5 pph.

Typical prior art golf ball cores incorporate 5 to 50 pph of zinc oxidein a zinc diaciylate-peroxide cure system that cross-links polybutadieneduring the core molding process. However, in the present invention it ispreferred that the zinc oxide (“ZnO”) in the core composition iseliminated in favor of calcium oxide (“CaO”). Cores produced from anadmixture containing CaO have been found to exhibit desirableperformance properties. In particular, when ZnO is replaced with CaO, ithas been observed that the initial velocity and COR of the core ismaintained, but the compression of the core is reduced by at least about4 compression points on the standard compression scale, and may bereduced as much as 6 points. Additionally, the combination of the use ofcalcium oxide and a higher percentage of zinc diacrylate can be used tomaintain the same compression as with the zinc oxide, but the initialvelocity and COR is significantly increased. Thus, by using calciumoxide, either the core compression can be lowered and the initialvelocity and COR maintained or the amount of zinc diacrylate can beincreased so that the core compression is the same and the initialvelocity and COR is increased.

Typically the calcium oxide added to the core-forming compositionemployed in the present invention is in the range of about 0.1 to 15,preferably 1 to 10, most preferably 1.25 to 5, parts calcium oxide perhundred parts (pph) of polybutadiene.

The core compositions employed in the present invention may also includefillers, added to the elastomeric composition to adjust the densityand/or specific gravity of the core. As used herein, the term “fillers”includes any compound or composition that can be used to vary thedensity and other properties of the subject golf ball cores. Fillersuseful in the golf ball core according to the present invention include,for example, zinc oxide (in an amount significantly less than that whichwould be necessary without the addition of the calcium oxide), bariumsulfate, and regrind (recycled core molding matrix ground to 30 meshparticle size). The amount and type of filler utilized is governed bythe amount and weight of other ingredients in the composition, since amaximum golf ball weight of 1.620 ounces (45.92 gm) has been establishedby the USGA. Appropriate fillers generally used range in specificgravity from about 2.0 to 5.6. In the preferred golf ball, the amount offiller in the core is lower than that of a typical golf ball such thatthe specific gravity of the core is decreased.

The preferred range of specific gravities of the cores employed in thepresent invention is from about 1.0 to about 1.2, more preferably in therange of about 1.1 to about 1.18, depending upon the size of the core,cover, intermediate layer and finished ball, as well as the specificgravity of the cover and intermediate layer.

Other ingredients such as accelerators, e.g. tetra methylthiuram,processing aids, processing oils, plasticizers, dyes and pigments,antioxidants, as well as other additives well known to the skilledartisan may also be used in the present invention in amounts sufficientto achieve the purpose for which they are typically used.

The intermediate layer, cover inner layer, or both, of the golf balls ofthe present invention are formed from a blend which includes a glycidylpolymer. The glycidyl polymer can be selected from a group including atleast one of a homopolymer, a copolymer, a terpolymer, or a mixturethereof. The homopolymer produced from a repeat unit containing aglycidyl group is of the form:

wherein R₁ is hydrogen, CH₃, linear or branched alkyl group having theformula C_(x)H_(2x+1) where x is an integer from 1 to about 8, aromatic,or alicyclic;

R₂ is hydrogen, CH₃, linear or branched alkyl group having the formulaC_(y)H_(2y+1) where y is an integer from 1 to about 20, aromatic, oralicyclic; and

n is an integer ranging from 1 to about 6.

The copolymer containing, a glycidyl group is of the form:

wherein R₃, R₄, and R₅ are hydrogen, CH₃, linear or branched alkyl grouphaving the formula C_(x)H_(2x+1), where x is an integer from 1 to about8, aromatic, or alicyclic;

R₆ is hydrogen, CH₃, linear or branched alkyl group having the formulaC_(y)H_(2y+1) where y is an integer from 1 to about 20, aromatic, oralicyclic;

o ranges from about 1 to about 99 weight percent of the total polymer;

p ranges from about 99 to about 1 weight percent of the total polymer;and

q is an integer ranging from 1 to about 6.

The terpolymer containing a glycidyl group is of the form:

wherein R₇, R₈, R₉, and R₁₁ are hydrogen, CH₃, linear or branched alkylgroup having the formula C_(x)H_(2x+1) where x is an integer from 1 toabout 8, aromatic, or alicyclic;

R₁₀ and R₁₂ are hydrogen, CH₃, linear or branched alkyl group having theformula C_(y)H_(2y+1) where y is an integer from 1 to about 20,aromatic, or alicyclic;

r ranges from about 1 to about 99 weight percent of the total polymer;

s ranges from about 1 to about 50 weight percent of the total polymer;

t ranges from about 1 to about 30 weight percent of the total polymer;and

u is an integer ranging from about 1 to about 6.

Examples of alkyl groups include lower alkyl, for example, methyl,ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl or tert-butyl; higheralkyl, for example, octyl, nonyl, decyl, and the like. One of ordinaryskill in the art is familiar with numerous linear and branched alkylgroups which are within the scope of the present invention.

Examples of glycidyl polymers include various types of resins such asethylene-glycidyl methacrylate copolymer, ethylene-glycidylmethacrylate-methyl acrylate terpolymer, and ethylene-glycidylmethacrylate-methyl vinyl acetate terpolymer. Commercially availableglycidyl polymers are ELVALLOY, from DuPont of Wilmington, Del., andLOTADER from Elf-Atochem, of Philadelphia, Pa.

In a preferred embodiment of the present invention, the intermediatelayer is formed from a blend which comprises glycidyl polymer and asecond component which comprises a thermoplastic material. Suitablethermoplastic materials for use in the intermediate blend include, butare not limited to, polyesterester block copolymers, polyetheresterblock copolymers, polyetheramide block copolymers, ionomer resins,dynamically vulcanized thermoplastic elastomers, hydrogenatedstyrene-butadiene elastomers with functional groups such as maleicanhydride or sulfonic acid attached, thermoplastic polyurethanes,thermoplastic polyesters, polymers formed using a metallocene catalyst(“metallocene polymers”) and/or blends thereof.

Suitable thermoplastic polyetheresters include materials which arecommercially available from DuPont of Wilmington, Del., under thetradename HYTREL and include HYTREL 3078, HYTREL G3548W and HYTRELG4078W. Suitable thermoplastic polyetheramides are commerciallyavailable from Elf-Atochem of Philadelphia, Pa., under the tradenamePEBAX and include PEBAX 2533, PEBAX 1205 and PEBAX 4033. Suitablethermoplastic ionomer resins include any number of olefinic basedionomers such as SURLYN (DuPont) and IOTEK (Exxon). Suitable dynamicallyvulcanized thermoplastic elastomers include SANTOPRENE, SARLINK, VYRAM,DYTRON, and VISTAFLEX. SANTOPRENE is the trademark for a dynamicallyvulcanized PP/EPDM. SANTOPRENE 203-40 is an example of a preferredSANTOPRENE and is commercially available from Advanced ElastomerSystems. Examples of suitable functionalized hydrogenatedstyrene-butadiene elastomers having functional groups such as maleicanhydride or sulfoniic acid, include KRATON FG-1901x and FG-1921x, whichare commercially available from the Shell Corporation. Examples ofsuitable thermoplastic polyurethanes include ESTANE 58133, ESTANE 58134and ESTANE 58144, which are commercially available from the B.F.Goodrich Company of Cleveland, Ohio. Suitable metallocene-catalyzedpolymers, i.e., polymers formed with a metallocene catalyst, includethose commercially available from Sentinel Products of Hyannis, Mass.Suitable thermoplastic polyesters include poly(butylene terephthalate),poly(ethylene terepthalate), and poly(trimethylene terepthalate).

Preferably, the second component of the intermediate layer blendcomprises polyetherester block copolymer, with HYTREL 3078 being aparticularly preferred polyetherester block copolymer.

Generally, many prior art intermediate layers have a specific gravity ofabout 1 or less. However, in a preferred embodiment, the intermediatelayer employed in the golf balls of the present invention has a specificgravity greater than 1.2, preferably about 1.21 to about 1.30, morepreferably about 1.23 to about 1.29 and most preferably about 1.27.

The desired specific gravity of the intermediate layer may be obtainedby adding a filler such as barium sulfate, zinc oxide, titanium dioxideand combinations thereof to the intermediate layer blend. Zinc oxide isthe preferred filler.

The intermediate layers of the present invention are formed from anintermediate layer blend comprising up to 100 percent by weight ofglycidyl polymer. In a preferred embodiment of the present invention,the intermediate layer is formed from a blend of about 1 to about 99percent by weight of a glycidyl polymer, about 0 to about 75 percent byweight of the second thermoplastic component (as describe above) andabout 0 to about 50 percent by weight zinc oxide. In one embodiment ofthe present invention, the intermediate layer is formed from a blend ofabout 10 to 50 percent by weight glycidyl polymer, 25 to 75 percent byweight of a second thermoplastic component and about 5 to about 40percent by weight zinc oxide. In a most preferred embodiment of thepresent invention, the intermediate layer is formed from a blend ofabout 15 to about 30 percent by weight glycidyl polymer, about 40 toabout 70 percent by weight of a second thermoplastic component and about15 to about 30 percent by weight zinc oxide. In another embodiment ofthe invention, the second thermoplastic component is present in theintermediate layer blend in an amount of less than about 65 percent byweight, and preferably about 55 to 63 percent by weight.

The intermediate layer blend preferably has a flexural modulus of lessthan about 10,000 psi, more preferably about 5,000 to about 8,000 psiand most preferably about 7,500 psi. Likewise, the intermediate layersemployed in the golf balls of the present invention preferably have aShore D hardness of about 25 to 50, and more preferably about 27 toabout 40.

The intermediate layers employed in the golf balls of the presentinvention preferably have a thickness from about 0.020 inches to about0.125 inches, more preferably about 0.035 inches to about 0.085 inchesand most preferably about 0.06 inches The outer diameter of theintermediate layer is preferably about 1.510 to 1.580 inches.

The cover layer of the present invention comprises at least one layer ofa thermoplastic or thermosetting material. Any number of a wide varietyof cover materials may be used in the present invention, such as lonomerresins, polyurethanes, balata and blends thereof, with ionomer resinsbeing preferred.

Ionomers, such as acid-containing ethylene copolymer ionomers, includeE/X/Y copolymers where E is ethylene, X is a softening comonomer such asacrylate or methacrylate present in 0-50 (preferably 0-25, mostpreferably 0-2), weight percent of the polymer, and Y is acrylic ormethacrylic acid present in 5-35 (preferably 10-35, most preferably15-20) weight percent of the polymer, wherein the acid moiety isneutralized 1-90% (preferably at least 40%, most preferably at leastabout 60%) to form an ionomer by a cation such as lithium, sodium,potassium, magnesium, calcium, barium, lead, tin, zinc or aluminum, or acombination of Such cations, lithium, sodium and zinc being the mostpreferred. Specific acid-containing ethylene copolymers includeethylene/acrylic acid, ethylene/methacrylic acid, ethylene/acrylicacid/n-butyl acrylate, ethylene/methacrylic acid/n-butyl acrylate,ethylene/methacrylic acid/iso-butyl acrylate, ethylene/acrylicacid/iso-butyl acrylate, ethylene/methacrylic acid/n-butyl methacrylate,ethylene/acrylic acid/methyl methacrylate, ethylene/acrylic acid/methylacrylate, ethylene/methacrylic acid/methyl acrylate,ethylene/methacrylic acid/methyl methacrylate, and ethylene/acrylicacid/n-butyl methacrylate. Preferred acid-containing ethylene copolymersinclude ethylene/methacrylic acid, ethylene/acrylic acid,ethylene/methacrylic acid/n-butyl acrylate, ethylene/acrylicacid/n-butyl acrylate, ethylene/methacrylic acid/methyl acrylate andethylene/acrylic acid/methyl acrylate copolymers. The most preferredacid-containing ethylene copolymers are ethylene/methacrylic acid,ethylene/acrylic acid, ethylene/(meth)acrylic acid/n-butyl acrylate,ethylene/(meth)acrylic acid/ethyl acrylate, and ethylene/(meth)acrylicacid/methyl acrylate copolymers.

The manner in which these ionomers are made is well known in the art asdescribed in e.g. U.S. Pat. No. 3,262,272. As mentioned above, ionomerresins are commercially available from DuPont of Wilmington, Del., underthe tradename SURLYN, and Exxon under the tradename IOTEK.

As is well known in the art, ionomer resins may be blended in order toobtain a cover having desired characteristics. For this reason, it ispreferable that the covers of the golf balls of the present invention beformed from a blend of two or more ionomer resins.

A particularly preferred cover material for use in the present inventionis formed from a blend of about 50 percent by weight SURLYN 7940, about47 percent by weight SURLYN 8940 and about 3 percent by weight SURLYN8660.

The cover layers employed in the present invention preferably have aShore D hardness of about 54 to about 72, more preferably about 65 toabout 70 and most preferably about 68 to about 70.

It should be understood that the composition of any of the above layers,such as core layers, intermediate or mantle layers, or cover layers, mayinclude additives, such as pigments, foaming agents, inert/reactivefillers, including ceramic spheres, glass spheres, etc., as would bereadily determined by one of ordinary skill in the art.

The multi-layer golf ball of the invention can have an overall diameterof any size. Although the United States Golf Association (USGA)specifications limit the minimum size of a competition golf ball to1.680 inches in diameter or more, there is no specification as to themaximum diameter. Moreover, golf balls of any size can be used forrecreational play. The preferred diameter of the present golf balls isfrom about 1.680 inches to about 1.800 inches. The more preferreddiameter is from about 1.680 inches to about 1.760 inches. The mostpreferred diameter is about 1.680 inches to about 1.740 inches.

The golf balls of the present invention have an overall maximumcompression of about 90, preferably about 75 to about 85, morepreferably about 80 to about 85 and most preferably about 82.

The golf balls of the present invention can be made by any conventionalprocesses employed in the golf ball art. For example, the solid corescan be either injection or compression molded. The intermediate layer issubsequently injection or compression molded about the core. It isimportant that the intermediate layer material be able to sustain thetemperatures applied during the application of the cover layer. Thecover layer or layers are then injection or compression molded or castabout the intermediate layer.

EXAMPLES

The cores of multi-layer balls were formed by compression molding ablend of the batch fomulation set forth in Table 1 below.

TABLE I Core Batch Formulation Parts Material Per Hundred Polybutadiene(Cariflex 1220) 76.00 Rubber (Neocis BR-40) 24.00 Pigment 0.10 ZincDiacrylate 24.79 Calcium Oxide 2.16 Regrind 6.47 Peroxide (Varox 231 XL)0.43 Peroxide (Elastochem DBDB EF-60) 0.16 Filler 22.64 Process Oil 1.50

All of the cores had a diameter of about 1.39 inches and were measuredto have compressions ranging from about 45 to 55 and specific gravitiesof from about 1.134 to 1.146. For the above core batch formulation, theresultant cores were measured to have a compression of 48. Theintermediate layer blends of Table 2 were subsequently injection moldedabout the cores of Table 1 to form the intermediate layers of the ballshaving an outer diameter of about 1.51 inches.

TABLE II Intermediate Layer Formulation Example 1 Example 2 Example 3Control Formulation (weight %) (weight %) (weight %) (weight %) Hytrel3078¹ 59 59 59 59 Nucrel 960² — — — 20 Zinc oxide 21 21 21 21 Lotader8900³ 20 — — — Lotader 8930⁴ — 20 — — Lotader 8920⁵ — — 20 — ¹blockcopoly(ether-ester) elastomer, from DuPont, having a Shore D of about30. ²ethylene-methacrylic acid copolymer, from DuPont, having a Shore Dof 46. ³ethylene-23.5 wt. % methyl acrylate-7.25 weight percent glycidylmethacrylate terpolymer, from Elf-Atochem, having a Shore A of 70.⁴ethylene-26 wt. % methyl acrylate-1.0 weight percent glycidylmethacrylate terpolymer, from Elf-Atochem. ⁵ethylene-24.0 wt. % methylacrylate-3.0 weight percent glycidyl methacrylate terpolymer, fromElf-Atochem, having a Shore A of 75.

All of the multi-layer balls had a cover composition formed bycompression molding a blend comprising 50% SURLYN 7940 and 50% SURLYN8940 and a sufficient amount of titanium dioxide concentrate about theintermediate layers and were subsequently finished using conventionalclear coating and buffing techniques. The finished golf balls had anouter diameter of about 1.68 inches. These balls were tested for initialvelocity, compression, cover hardness, and COR, the results of Suchtests are set forth in Table 3 below.

As can be seen in Table 3, both mantle layers and golf balls preparedaccording to the present invention, shown as the compositions presentedin Examples 1-3 in Table 2 above, exhibit low compression, i.e., soft“feel”, while retaining high initial velocity or COR.

TABLE III Mantle Layer and Ball Properties Example 1 Example 2 Example 3Control Mantle Properties Hardness¹ 32 33 31 38 Compression 47 47 47 51COR² 0.758 0.756 0.757 0.762 Ball Properties Cover Hardness¹ 67 67 67 67Compression 76 75 75 81 COR² 0.792 0.788 0.792 0.798 Initial Velocity(ft/s) 251.1 251.1 251.0 251.2 ¹Shore D hardness ²Adjusted COR at 125ft/s incoming velocity

We claim:
 1. A golf ball comprising: a core having a compression of nogreater than about 90; a cover layer having a Shore D hardness of about54 to 79; and at least one intermediate layer disposed between the coverand the core, wherein the at least one intermediate layer is formed froma blend comprising about 10 to 50 percent by weight glycidyl polymer andabout 25 to 75 percent by weight thermoplastic material, and wherein thegolf ball has a coefficient of restitution of greater than about 0.76.2. The golf ball of claim 1, wherein the golf ball has a compression ofno greater than about
 90. 3. The golf ball of claim 1, wherein thethermoplastic material is selected from the group consisting ofpolyesterester block copolymers, polyetherester block copolymers,polyetheramide block copolymers, dynamically vulcanized thermoplasticelastomers, styrene-butadiene elastomers, thermoplastic polyurethanes,thermoplastic polyesters, polymers formed using a metallocene catalyst,and blends thereof.
 4. The golf ball of claim 3, wherein thethermoplastic material comprises a polyetherester block copolymer. 5.The golf ball of claim 3, wherein the blend further comprises a fillerin an amount sufficient to provide the at least one intermediate layerwith a specific gravity of greater than about 1.2.
 6. The golf ball ofclaim 5, wherein the at least one intermediate layer has a specificgravity of greater than about 1.25.
 7. The golf ball of claim 6, whereinthe filler comprises zinc oxide.
 8. A golf ball comprising: a corehaving a compression of no greater than about 90; a cover layer having aShore D hardness of about 54 to 72; and at least one intermediate layerdisposed between the cover and the core, wherein the at least oneintermediate layer is formed from a blend comprising about 10 to 50percent by weight glycidyl polymer, about 25 to 75 percent by weightthermoplastic material, and about 5 to 40 percent by weight filler, andwherein the golf ball has a coefficient of restitution of greater thanabout 0.76.
 9. The golf ball of claim 8, wherein the blend comprisesabout 15 to 30 percent by weight glycidyl polymer, about 40 to 70percent by weight second thermoplastic component and about 15 to 30percent by weight filler.
 10. The golf ball of claim 8, wherein the golfball has a compression of no greater than about
 90. 11. The golf ball ofclaim 1, wherein the cover comprises at least one of a thermoplastic ora thermoset material.
 12. The golf ball of claim 8, wherein the filleris present in an amount sufficient to provide the at least oneintermediate layer with a specific gravity of greater than about 1.2.13. The golf ball of claim 8, wherein the filler comprises zinc oxide.14. The golf ball of claim 12, wherein the at least one intermediatelayer has a specific gravity of greater than about 1.25.
 15. A golf ballcomprising: a core comprising polybutadiene; a cover layer having aShore D hardness of about 54 to 72; and at least one intermediate layerdisposed between the cover and the core, wherein the at least oneintermediate layer is formed from a blend comprising: about 15 to 30weight percent of a glycidyl polymer; about 15 to 30 weight percent zincoxide; up to about 70 weight percent polyetherester block copolymer; andwherein the golf ball has a coefficient of restitution of greater thanabout 0.78.
 16. The golf ball of claim 15, wherein: the core furthercomprises calcium oxide; and the intermediate layer is formed from ablend comprising: about 19 to 21 weight percent glycidyl polymer; about20 to 22 weight percent zinc oxide; and about 58 to 60 weight percentpolyetherester block copolymer.
 17. The golf ball of claim 15, whereinthe intermediate layer has a Shore D hardness of less than about 40 anda flexural modulus of less than about 10,000 psi.
 18. The golf ball ofclaim 15, wherein the blend comprises at least about 40 weight percentpolyetherester block copolymer.
 19. A golf ball having a coefficient ofrestitution of greater than about 0.7 and a compression of at leastabout 50, wherein the ball comprises a core and a cover comprised of atleast one layer disposed concentrically about the core, wherein thelayer is a composition comprising a glycidyl polymer composition and athermoplastic selected from the group of copolyesters, polyamides,polyetherester block copolymers, polyesterester block copolymers,polyetheramide block copolymers, polyesteramide block copolymers, andpolyurethane, wherein the glycidyl polymer composition comprises arepeat unit of formula

wherein R7, R8, R9, and R11 are hydrogen, linear or branched alkyl grouphaving the formula CxH2x+1, aromatic, or alicyclic, where x is aninteger from 1 to about 8; R10 and R12 are hydrogen, linear or branchedalkyl group having the formula CyH2y+1, aromatic, or alicyclic, where yis an integer from 1 to about 20; r ranges from about 1 to about 99weight percent of the total glycidyl polymer; s ranges from about 1 toabout 50 weight percent of the total glycidyl polymer; t ranges fromabout 1 to about 30 weight percent of the total glycidyl polymer; and uis an integer ranging from about 1 to about 6, and wherein thecomposition has a flexural modulus less than 20,000 psi.
 20. The golfball of claim 19, wherein the composition further comprises a fillersufficient to produce a specific gravity of greater than about 1.2. 21.The golf ball of claim 19, wherein the cover is comprised of an outerlayer and an inner layer and the composition forms the inner layer. 22.The golf ball of claim 21, wherein the inner layer has a first hardnessand the outer layer has a second hardness greater than the firsthardness.
 23. The golf ball of claim 22, wherein the core has a thirdhardness within 10 Shore D of the first hardness and less than thesecond hardness.
 24. The golf ball of claim 21, wherein the inner layerhas a specific gravity greater than about 1.2.
 25. The golf ball ofclaim 21, wherein the inner layer has a flexural modulus of less thanabout 10,000 psi.